engine harshness at high revs
 

Im referring to some articles I read on the internet regarding engine harshness at high rpms. Does this seem to be an issue for anyone? If this is an issue, is it something that can be worked out with different engine tuning (COBB) or is it a mechanical issue?

I haven't driven many other high performance cars, but I did get some time on a track in both an Audi RS4 and an Audi R8. I don't think the 370Z is any more harsh at high revs than either of the Audis. Contrary to what the reviewers say, I like the feel speed and power at high revs which is only supplemented more by some vibration or thunder under the hood...it's exhilarating. Don't worry about those reviews and especially don't let it stop you from buying a 370.

I agree. I guess if you have driven many great sports cars, it could bother you a little bit. Some of those reviewers are way too picky - many complained about noise from the wheel wells, and a rough ride, but the 370z had a softer, quieter ride than my Saan 9-3!

Our car is very rough at high RPM's...I've been in a few cars that should be rougher per se, but are smooth as silk compared to this. Nissan lost points in the refinement department with this engine...

I'm guessing you're referring to noise harshness? I agree, but I kinda like it. It sounds very "raw".

everything, its gotta a very coarse feeling to it. Everything vibrates and sounds like its not supposed to be revving that high. Its something I've learned to live with, but it should not be this way. I wonder if its an engine mounts thing....

i was thinking the exact same thing, but they have 4 mounts including some liquid filled ones right? I can't imagine nissan missing the calculations with the mounts tho....just doesn't sound like something that would happen.

If you take a Porsche flat six or a Chevy LSx V8 to the rev limiter, it sounds like a beautiful, hard working sports car engine that builds like a crescendo all the way to the fuel cutoff, both inside the car and out.

The 370z has a muted exhaust tone that has the overall boring soundtrack of the vq engine that we all know from Muranos, Altimas, etc, but with some of the qualities of the 70's straight sixes. You get that sound up until 5,000 rpm or so when the cacaphony of engine clatter starts to become as loud as the exhaust. An aftermarket exhaust helps that, but overall, it's still pretty noisy under the hood. A similar ammount of vibration is transmitted back through the steering, pedals and shifter, but for me, it's mostly the noise.

Can't take it too personally, with a car as great as the Z, they really have to dig to come up with "cons"

I too like the high-rpm coarseness on the 370Z. Most people that have ridden in the car like it as well. For me, it seems that once you get over 6500rpms is when engine noise is rather intrusive. I don't know, but it would stand to reason that this is partly due to the VVEL. If you think about it, valve lift/duration increases with revs, so essentially, the VVEL allows more and more air/fuel into the engine the higher you rev it, so it would only make sense that more power = more noise.

Either way, it almost has a different character in the high rpms/sounds like a different engine.

The one thing that DID surprise me about the powertrain is how much it sounds like a 4-banger. LOL. The engine just doesn't have the typical V6 smoothness that I was use to from my 2007 Altima 3.5SE. That's comparing apples to oranges, but you'd still expect a slight resemblance considering they're both Nissan V6's. But not so much.

Late,
Trav

6SPD_FTW no offense, but your logic is flawed from the start. "more power = more noise" that is not necessarily true.

I hope people dont misunderstand me, I'm not arguing whether i like it or I dont or whether you like it or you dont. All I am saying is that the motor makes a lot of noise and vibration at high rpm. I find reviewers' "pickiness" about the coarseness of this motor perfectly understandable. The motor should NOT feel like its going to spin itself apart at high rpm. There's no excuse for this. For those of you that say "its a sports car, it comes with the terrictory" I beg to differ. The GT3RS is much more of a sports car, almost a dedicated track car and even past 8k RPM that engine is completely smooth.

It may have something to do with the VVEL, no doubt about that.

A lot of reviews I've read concerning the VQ engine say the same thing. It's not isolated to our car, it's the VQ in general. It is rougher than other engines and I would love for it to be smoother but you do get used to it.

I actually work for an Audi dealership and have driven over a dozen R8s (track training) and a few RS4s along with owning the newest TT model (VR6) and driven all the other RS and S models and those engines are all 10 times smoother at higher RPMs then the Z. I had to get used to that about this car after purchase. But your also paying a huge difference in cost for those cars. That alone keeps me smiling!! I've also noticed that as the break in takes place the harshness subsides a bit. :tup:

I don't know about everything else, but I can agree with that.

I agree, it feels like the engine is going to slap me in the face past 6500 rpm. I think the reviewers were well in line when they complained about the harshness, picky or not. Lets me honest here. Love the car BIGTIME, but it is harsh.

I have heard[don't know true or false],our cars comes with a active electronic controlled engine mounting,maybe it becomes harder when the revs rise above a certain Rpm,can anyone comfirm this.?

I don't think this is true. I looked in the Service Manual at the exploded view, they show the engine mounts (there's 3, one on each side and one at the rear), and there's no indication of any kind of electrical (or other) connections to them, they're just standard rubber/urethane/whatever mounts.

This motor is a tad more coarse IMO than the HR. The HR was *much* more so than my Revup, which itself isn't as smooth as the normal VQ35DE. And I've heard from owners that moved up from the VQ30 to the VQ35 that the VQ30 was much smoother as well.

It appears to be a negative trend spanning nearly over a decade now.

so we have some weird liquid filled engine mounts right? I wonder if Nissan did this to cover up the harshness/vibration...

The new 911 GT3 uses weird liquid filled engine mounts (as an available option), but they are talking about them as a point of pride because it's a technological breakthrough, rather than trying to cover it up.

SRT-4 owners complained about the harshness of the muffler-less exhaust and the harshness of the turbo kicking in when they first picked up their cars. But that's why people purchased the car.

Hey, it sounds better than the Ford Focus I drove before it, so I'm not that bothered.

I wonder if there's some variance in our engines, or perhaps it quiets down after sufficient break-in? Mine's a little harsh, but after hearing you guys complain about it, it makes me wonder if we're hearing the same things or not. Mine's not really that bad. I'm at just a hair under 7K miles now, and I guess 7AT could make a difference too, as the torque converter / trans will damp engine vibration differently than your flywheel/clutch setup will.

Interesting, as I also have the 7AT (I would have loved to get a manual, but driving one in Los Angeles is brutal, so I sissy'd up and got the auto) and don't find it annoying at all.

wstar, your car doesnt vibrate at high rpm?

Well, it certainly sounds quite loud and raw up around 6-7.5K, and I could see how some would call it unrefined, but I wouldn't say the car is vibrating in a really noticeable way, and doesn't seem as bad as some people seem to be making it here. Are you feeling that through the steering wheel, pedals, shifter, etc? Tomorrow if the rain is gone I'll go for a drive in the morning and specifically pay attention for it so I can compare.

I think maybe the M6 guys feel it more than the 7ATs. I get a lot of that coarse feedback not only from the seat but from the gearbox and the clutch as well.

I am willing to deal with it but it does irk me every now and then considering the test drives I did with the Cayman S... so every now and then I think about how silky smooth that engine feels compared to the Z. But thinking about the price differential usually kills any "should have bought the Cayman" thoughts.

Though it is funny, I think, that my '03 Mustang GT's 4.6L V8 was a lot smoother and a little more refined feeling than this V6. I'm not really a fan of the gearbox in the Z either so it kind of annoys me every now and then.

Maybe I'm just picky, though. I've pretty much accepted the fact that no matter what car I have I will never be totally happy with it.

maybe 6mt is a lot worse. I can feel it in the floor, shifter, steering wheel. I've noticed the transmission mounts need some serious work too. The mounts are too soft.

Hmmm, I tried to pay better attention this morning, but no I don't think I'm getting vibration like you describe. It could be that your vibration is largely coming into the body though the clutch/transmission, and my torque converter is eating it up instead on the 7AT.

:iagree:

I have a 6MT and the whole car vibrates and almost feels like its going to rip apart at any moment lol (slight exageration) at high rpms. You really do feel it in the floor, steerng wheel, shifter...even the seat to some extent.

Yeah, I definitely think the we 6MT guys feel it the most. You really feel the vibrations in the clutch pedal when you shift at high RPMs. We get feedback from the clutch pedal and the shifter that the 7AT guys aren't getting.

Usually for them it's two hands on the steering wheel and the feedback you get from the wheel seems mostly to be from the road.

I know at times pushing the clutch pedal in just feels downright nasty.

Likely this has to more to do with the natural imbalance of the V6, which has been exacerbated as they stroked the original VQ engine design more and more. Another engine recently revised with a longer stroke and VVEL is the VK50DE. How harsh is the VK50 in the FX50 at high rpms?

Edit: After finding Edmunds review, they stated that the VK50, 'much like VQ35/37 this V8 isn't quiet or smooth @ high RPM.' So we can rule that it's either the longer stroke, the VVEL or both.

So, the problem must be related to the engine since it is noticeable in both the 6MT and 7AM (I know more in the 6MT but that doesnt matter).

Was this problem noticed in the 350z? Someone mentioned the VQ35DE was smooth. I am not familiar with engine names, but is that the 350z engine?

To me, the problem seems like its related to the VVEL. Do the vibrations increase gradually as you rev higher or is it an instant thing? Has anyone driven a Honda with VTEC? VTEC kicks in full force at a certain rpm. Its like a whole nother engine. The intake seems 17 times louder than before VTEC kicks in and the whole car becomes harsher. Does it seem something like that? If so and the vibrations really kick in all at once at a certain rpm, then we can confirm that it is something related to the VVEL. If not, maybe it is an imbalance in the crankshaft or camshaft, something rotating.

If the mounts were firmer, wouldn't you be getting alot MORE vibration? Engine movement would be directly transfered to the entire chassis.

http://farm1.static.flickr.com/211/4...74bd9674db.jpg

Our glorified vtec might be responsible for the vibration...

Yes sir, but thats not the reason why I want harder mounts. I just feel the transmission mounts flexing and the shifts could be a lot more "positive" with some bushings. The car will feel a little crisper response if you remove the flex in the tranny.

Yeah thats true. And usually with stiffer mounts you feel it more at idle. Since it seems like this problem isnt noticed at idle, the harshness must be more than just the mounts.

It's really a gradual thing. It gets worse as you go up in revs. It's nothing like the VTEC transition where at a given RPM *bam* you have a new engine.

VVEL may or may not have something to do with it, but I'd venture to guess that it probably isn't the root cause. It's probably just how the engine naturally behaves and we just have to deal with it. It's definitely wierd, though, because it doesn't feel right when you drive the car hard... but it probably is right. Just have to get used to it I guess.

The electronically controlled motor mounts are usually 'soft' at <950rpm and
'hard' at >950rpm. The VQ35DE in the Altima/Maxima/Murano has a vacuum/solenoid controlled system that softens the mounts at idle and hardens them at speed. The 370Z doesn't have this system. There's vacuum tubes that lead to the motor mounts that would be there and they aren't on the Z.

Dunno bout fluid-filled mounts, though. Nissan used fluid-filled mounts on the transmission and front (side) motor mount on the Altima VQ. Judging by the harshness of the Z, I'd doubt there are any fluid-filled mounts on this car.

Late,
Trav

It's largely an inherent property of the engine. A V6 is not inherently balanced. Neither is an inline 4 cyl, a boxer 4 cyl is.

Straight 6 cyl and 90 degree v8s are inherently balanced also. That's partly why BMW uses straight sixes and refers to a V6 as a bent six.

When u take a motor that's not inherently balanced and give it large pistons and a long stroke (high velocity), it's going to vibrate a lot. You must then add counter weights to smooth things out, but that robs power and increases complexity. They can be made smooth ie NSX, but it's not easy.

I have an M3 and a 335, and they're smoth as silk. Coming from that, the VQ37 feels VERY harsh.

You can't compare the vq37 to the v8 because the v8 is an inherently balanced configuration.

I could explain in much more detail, but I'm typing on my iPhone